The article discusses two provisions--least restrictive environment and the individualized education program--generated by P.L. 94-142, Education for All Handicapped Children Act. Priorities for effective mainstreaming are considered, and opposition to the least restrictive environment concept is examined. It is concluded that the key to P.L. 94-142 is threefold: (1) that schools assess each child's ability, (2) that schools design an individualized education program that meets the child's educational needs, and (3) that schools assure that parental participation and due process procedures become components in all phases of the undertaking. (SBH)